If you have ever measured the temperature of melting ice, you would have noticed that the temperature keeps rising till it reaches 0 degree C, when the temperature remains stable and the ice starts melting. Only when all the ice has melted does the temperature rise again. It needs some heat energy to go from ice at 0 degree C to water at 0 degree C. This energy is called the latent heat of fusion. See, much more simple, and without involving nucleation points 😀